Every summer, Stream Team volunteers stir things up looking
for “stream bugs”. These critters, otherwise known as benthic
macroinvertebrates, provide valuable information about water
quality and the biological health of streams. They are also fun
to collect and examine.

After all the samples are gathered, they are sent to a lab
where they are assessed according to a
Benthic Index of Biological Integrity (BIBI). This index
gives a biological health rating for our streams (low, medium or
high biological integrity), as well as other important
information regarding what may be impacting the health of our
streams. Currently, Stream Team volunteers gather samples from
twenty streams throughout Thurston County.

What are benthic macroinvertebrates?

Benthic macroinvertebrates are critters that do not have a
backbone and live part or all of their lives in the bottom of
streams. They can include snails, aquatic worms and arachnids,
clams, crustaceans (like crayfish and shrimp), and insects. Some
are tolerant of pollution or habitat disturbance in the stream,
and some are sensitive to pollution and habitat disturbance.

“Stream bugs” are excellent indicators of stream health
because:

they are relatively sedentary (therefore they cannot
easily swim away from pollution);

they exhibit tolerance or intolerance to impacts to
streams; and

they are fairly easy to collect.

If you go: What to Expect

Before going out to gather the samples, volunteers attend a
weekday evening training (held two separate times in mid-late
June or early July). During the training, volunteers learn how
and why stream bugs are used to assess stream health, as well as
the monitoring protocol.

Volunteers can choose to monitor one or more sites. Each
monitoring site is led by a trained staff person. On average, it
takes about 3 to 5 hours to gather the samples and prepare them
to be mailed off to a lab. A variety of monitoring dates and
times are offered during the weekday, in the evenings, or on
weekends to accommodate people’s busy schedules.

Monitoring sites vary in accessibility: a few sites require
climbing down steep terrain and/or climbing over downed trees.
Volunteers help carry equipment to the monitoring location.
Waterproof boots or sandals are recommended. Sunscreen or insect
repellent may be useful for some sites.

For more information, including questions about monitoring
locations and accessibility, contact Ann Marie Pearce at
pearcea@co.thurston.wa.us or
360-754-3355 ext. 6857.